The present invention relates to a voltage level detector, and more particularly to an embedded voltage level detector for use between a power supply apparatus and a functional circuit.
A power supply apparatus is widely used to provide a working circuit with reliable power. The working circuit comprises many electronic devices, for example semiconductor memory devices or microprocessors, requiring a stable voltage. Therefore, the unstable voltage level of the supplied power will adversely affect the performance of the working circuit. Accordingly, a voltage level detector is provided between the power supply apparatus and the working circuit for detecting the voltage level of the supplied power. Then, measures will be taken when an unstable voltage is detected.
Referring to FIG. 1, a voltage level detector 12 is electrically connected with a power supply apparatus 10 and a working circuit 11. The conventional voltage level detector 12 comprises a voltage regulating circuit 121, a voltage comparing circuit 122 and a voltage dividing circuit 123. The voltage regulating circuit 121 receives and processes an input voltage V1 from the power supply apparatus 10 via a pin IN, and outputs a stable voltage Vout to the working circuit 11 via a pin OUT. The voltage dividing circuit 123 comprises a first resistor R1 and a second resistor R2, both electrically connected to the voltage comparing circuit 122. The resistors R1 and R2 are also electrically connected to a pin DIN and a ground pin GND, respectively, as shown in FIG. 1. A relatively stable reference voltage Vref is divided by the voltage dividing circuit 123 to result in a voltage V2 equal to Vrefxc3x97R2/(R1+R2). The input voltage V1 is compared with the divided reference voltage V2 in the voltage comparing circuit 122. Once the input voltage V1 is lower than the voltage V2, it is determined that the power from the power supply apparatus 10 is unstable, and a warning signal will be asserted by the voltage level detector 12 via a pin DOUT to inform the working circuit 11.
Since the voltage level detector 12 as mentioned above is usually packaged as an independent integrated circuit (IC) chip, the cost related to package and test cannot be exempted from. In addition, such voltage level detector 12 comprises some analog circuits, which results in much power consumption.
It is an object of the present invention to provide a voltage level detector, which can be integrated into another IC chip so as to reduce the manufacturing and testing cost.
It is another object of the present invention to provide a voltage level detector, in which totally logic circuitry is employed to avoid large current passing therethrough, thereby minimizing power consumption.
In accordance with an aspect of the present invention, there is provided a voltage level detector for use between a power supply apparatus and a functional circuit. The voltage level detector comprises a power input terminal, a voltage dividing circuit and a logic operation circuit. The power input terminal is electrically connected to the power supply apparatus for receiving therefrom power of a first voltage. The voltage dividing circuit is electrically connected to the power input terminal for dividing the first voltage into a second voltage having a level lower than that of the first voltage but greater than a threshold voltage. The logic operation circuit is integrated with the functional circuit and having a first and a second input ends thereof electrically connected to the power input terminal and the voltage dividing circuit, respectively. According to the voltage level detector of the present invention, a warning signal is asserted to the functional circuit when the second voltage level drops below the threshold voltage.
In an embodiment, the logic operation circuit includes an AND gate.
In an embodiment, the voltage dividing circuit comprises a variable resistor for adjusting the second voltage.
In an embodiment, the voltage level detector of the present invention further comprises a sample and hold circuit. The sample and hold circuit is electrically and connected to the logic operation circuit for outputting the warning signal. Furthermore, the voltage level detector of the present invention comprises a refreshing circuit. The refreshing circuit is electrically connected to the sample and hold circuit for clearing an output of the sample and hold circuit.
In an embodiment, the voltage level detector of the present invention further comprises a ripple counter electrically connected to and disposed downstream of the logic operation circuit, and counting incrementally in response to the warning signal.
In an embodiment, the voltage level detector of the present invention further comprises a multiplexer electrically connected to the voltage dividing circuit, a reference voltage input terminal and the logic operation circuit, and selecting one of the second voltage and a reference voltage to be outputted in response to a selection signal. Furthermore, the voltage level detector of the present invention comprises a compensation resistor electrically connected among the multiplexer, the logic operation circuit and ground.
In an embodiment, the voltage level detector of the present invention further comprises a register electrically connected to the voltage dividing circuit for providing data to tune the second voltage.
In an embodiment, the voltage level detector of the present invention further comprises a resistor electrically connected between the power supply apparatus and the logic operation circuit for adjusting the second voltage.
In an embodiment, the voltage level detector is embedded in the integrated circuit having therein the functional circuit.
In an embodiment, the threshold value is a minimal input voltage value defined as a high level by the logic operation circuit. Alternatively, the threshold value is a maximal input voltage value defined as a low level by the logic operation circuit.
In accordance with another aspect of the present invention, there is provided a voltage level detector for use between a power supply apparatus and a functional circuit. The voltage level detector of the present invention comprises a power input terminal, a voltage dividing circuit and an AND gate. The power input terminal is electrically connected to the power supply apparatus for receiving therefrom power of a first voltage. The voltage dividing circuit is electrically connected to the power input terminal for dividing the the first voltage into a second voltage. The AND gate is integrated with the functional circuit and having a first and a second input ends thereof electrically connected to the power input terminal and the voltage dividing circuit, respectively, for receiving and operating the first and the second voltages according to a threshold value, thereby determining whether the power is in a stable state or not.
In an embodiment, the voltage level detector of the present invention further comprises a sample and hold circuit electrically connected to and AND gate for outputting a warning signal to the functional circuit when an output of the AND gate is pulled low.
The above objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which: